1. Field of the Invention
The present invention relates to a harvester for leafy vegetables and a process for harvesting leafy vegetables.
2. Description of the Related Art
Harvesting young or early growth leafy vegetables presents particular problems not found when harvesting other vegetables. By "leafy vegetables" it is meant that family of specialty lettuces and other leafy greens which, when mixed together for sale and consumption are sometimes referred to as "spring mix," "mixed greens," or "baby greens." For example, this includes lettuces, such as green romaine, red romaine, sierra, lola rosa, tango, green leaf, red leaf, little gem, red butter, read oak, red perella and green perella. It also includes greens such as arugula, maxine, red mustard, green mustard, spinach, tat tai, red chard and red russian kale. If such leafy vegetables are grown under certain conditions, the harvested produce can be certified as organically grown.
Harvesters are known for cutting some vegetables such as spinach, cabbage, watercress and the like. Recently, consumer demand has required harvesting a variety of lettuces at an early stage of growth while the leaves are small and close to the ground.
This has presented challenges unmet by mechanical harvesters and consequently all young leafy vegetables has been largely by hand.
One problem in mechanically harvesting leafy vegetables is that the plants are very small when harvested. This means that the leafy vegetables must be grown in rows or beds which are prepared to be as flat as possible. The widths of the beds are also dimensionally controlled as much as possible. A typical bed is either 40 inches or 42 inches wide, as measured from the center of furrows on either side of the bed. Separating each of the beds are furrows which allow the passage of the wheels of farm equipment used to cultivate, plant, maintain, and harvest the leafy vegetables. With such small plants, a harvester must be able to maintain the cutting mechanism approximately 1/4 inch off the surface of the bed.
Another problem is that the leafy vegetables are very tender. They are easily bruised by conventional harvesters. Bruised or damaged leafy vegetables are not saleable and must be discarded, reducing yield.
One conventional harvester uses a sickle cutter formed at the bottom of a double belted conveyer system. The bottom belt is made of a metal mesh and the top conveyer is made of a flexible material with "fingers" formed in layers on the flexible belt. The fingers hold the cut leafy vegetables in contact with the lower conveyer as the cut produce is conveyed up the conveyer to the discharge area. This is necessary so that wind, for example, does not blow the cut leafy vegetables off of the conveyer.
This arrangement has several deficiencies. First, the fingers, while flexible, tend to damage or bruise the delicate leafy vegetables, thereby reducing yield. The fingers tend to break and the entire conveyer must be removed and replaced with a new or repaired one. This is both expensive and time consuming. Also, the presence of the upper fingered belt makes it difficult to inspect and clean the area between the two conveyer belts.
Another problem occurs because of the trend towards the use of double size rows or beds in addition to standard size beds. The width of these beds is 80 inches, or double the width of a conventional 40 inch bed. Eighty inch beds eliminate every other furrow in comparison with a field of 40 inch beds. This increases the area of cultivatable land, and hence yield, up to 50% to 80%. No known harvester is presently available which can harvester 40 inch, 42 inch and 80 inch beds.
It is very important that when the "spring mix" is ultimately shipped to customers and consumers that it be clean and completely free of sticks, weeds, or other debris. Also, any bruised or damaged leafs must be eliminated. Cotyledon, the poorly formed embryonic underleaves, must also be eliminated. When harvesting leafy vegetables manually this can largely be done when the plants are selected and cut by the field worker. Existing harvesting techniques introduce undesirable amounts of debris and unwanted materials with the harvested leafy vegetables.